Ugi four component condensations using aldehydes with an asymmetric centre at C-2

Epimerisation of an aldehyde possessing a hydrocarbon substituent α to the carbonyl occurs in the Ugi four component condensation whereas, with either a benzyl or TBDMS ether at C-2 the stereochemical integrity is maintained. A deuterium isotope effect is observed and by carrying out the reaction in methanol–OD, deuterium can be introduced efficiently into C-3 of the condensation products.